1. Field of the invention
The present invention relates to refrigerated trucks and trailers (“reefers”) and, more particularly, to an auxiliary power device for refrigerated trailers that acts as a power source to the truck's cab when the truck is parked, thereby allowing operation of heaters, air conditioning, outlets (for TV, microwaves, etc.), engine block heaters, and battery chargers, all without idling the truck's engine.
2. Description of the Background
When truck drivers park their tractor-trailers to load or unload, sleep, eat, shower or catch up on paperwork, most of the time they leave their truck running to keep the engine block warm and to operate the cab's air conditioning, heat, TV, VCR, computer and/or microwave. Trucks across the country spend millions of hours parked, yet idling their engines, burning fuel and releasing harmful emissions into the atmosphere. This is extremely inefficient and market forces are increasingly weighted against this:                Diesel fuel prices are at an all time high ($2.60-3.60 per gallon)        The government is passing increasingly strict idling and emissions laws.        More and more energy-consuming amenities are being added to trucks to help the trucking industry find and retain quality drivers to man their fleets (they purchase optional creature comforts to enhance the driving experience). Driver comfort is imperative for improving moral, health benefits and reducing turnover.        The cost of new tractor-trailers is at an all time high. Therefore, engine longevity is key to maximizing truck life, and idle use should be minimized.        
Of all the trucks on the road today, approximately 40% are known as “reefers”, e.g., trucks that have a refrigeration capability. These reefers haul everything from frozen food to fresh produce. A typical reefer includes a truck cab pulling a refrigerated trailer that is cooled by a large and expensive diesel refrigeration unit. FIG. 1 is a photo of a conventional reefer, inclusive of a truck cab pulling a refrigerated trailer that is so cooled by diesel refrigeration unit 1. In this case the refrigeration unit 1 is a Thermoking® SB3 Smart Reefer diesel generator-powered unit mounted to the front of the trailer, with enlarged control panel 2 inset. The unit is powered by a diesel motor, which through a series of dampers, clutches, drive belts, shaft seals, and idler pulleys turns a compressor to cool the trailer. The control panel 2 is a microprocessor-based programmable logic controller that uses temperature control algorithms to regulate the air temperature.
Deltek™ hybrid diesel electric technology from Carrier Transicold™ offers a similar yet simplified design featuring an electric-driven sealed compressor. This unit likewise relies on a diesel motor, but is connected to a generator that powers an electric motor inside the compressor housing. While this unit eliminates certain mechanical parts (dampers, clutches, drive belts, shaft seals, and idler pulleys to turn the compressor), it merely improves the efficiency of the refrigeration system. Neither of the foregoing systems nor any other deliver any power to the cab.
Consequently, whether a tractor-trailer is on the road or parked, these refrigeration units are always left running to maintain a constant temperature inside the trailer. It would be greatly advantageous to harness the power already being generated by these refrigeration units to power the cab's amenities (air conditioning, heat, TV, VCR, computer and/or microwave). The cost savings derived from reduced engine idling time would be significant:
For example, if we assume that annual fuel reduction=number of gallons burned per hour (approx. 1.75 gal per hour)×daily idling average (approx. 8 hrs)×days in use per year (240)×average current price of diesel ($3 per gal)=total cost savings per year per truck (over $10,000.00). Moreover, the benefits would include reduced engine hours, wear and tear, and reduction of harmful emissions released into the earth's atmosphere each year.
The general concept of an auxiliary power device for a tractor-trailer is known. For example, U.S. Pat. No. 4,780,618 discloses a tractor-trailer power conversion circuit that can be selectively actuated to direct power to the tractor unit from an auxiliary power source such as refrigeration unit or a conventional DC generator mounted on the trailer. The '618 patent shows a conversion circuit that uses either the refrigeration unit or a DC generator as an auxiliary power source. Similarly, U.S. patent application No. 20050063121 discloses an electrical system that uses a primary and secondary power supply for providing power to a truck's cab while the truck's engine is turned off. In one embodiment, the secondary power supply includes a generator mounted on the truck itself.
The present invention accomplishes the foregoing with the addition of an auxiliary power supply comprising a small electric generator (or alternator-style generator as will be explained) that derives mechanical power from the refrigeration unit and supplies electrical power to the truck's cab, thereby allowing the driver to turn off the truck's engine and still enjoy all the creature comforts provided in today's modern trucks. This saves fuel, cutting emissions and reducing wear and tear.